光照下巨磁电阻氧化物的室温响应性质

实验测量了巨磁电阻锰氧化物的光吸收谱,研究了在波长为０．６３μｍ的Ｈｅ－Ｎｅ激光和波段λ＝８￣１４μｍ的红外辐射条件下,薄膜在室温下的光响应性质。通过分析光响应与高制频率、偏置电流的关系,讨论了光响应机理。     

脉冲超导薄膜激光诱导电势差研究

精准的电势差值可以保证脉冲激光诱导击穿超导薄膜的稳定性,为了计算出激光诱导击穿超导薄膜的电势差,提出了脉冲超导薄膜激光诱导电势差研究。选择TUrale-200型号的激光器和电势采集仪为实验设备,以Nb超导薄膜、Nb3Ge超导薄膜、NbN超导薄膜和Nb3Sn超导薄膜作为实验样本,基于激光诱导击穿超导薄膜的实验原理,利用最大值最小值标准化和z-score标准化法预处理实验数据,获取激光诱导击穿超导薄膜前后的电势差值。实验结果表明,当激发条件为554 nm时,激光诱导击穿Nb超导薄膜、Nb3Ge超导薄膜、NbN超导薄膜和Nb3Sn超导薄膜前后的电势差在500 V以内,满足激光诱导击穿超导薄膜的稳定性要求,当激发条件为1 108 nm时,激光诱导击穿Nb超导薄膜、Nb3Ge超导薄膜、NbN超导薄膜和Nb3Sn超导薄膜前后的电势差超过了600 V,无法满足超导薄膜对激光诱导击穿的稳定性要求。     

量子响应高温超导薄膜红外探测器

基于超导探测器具有量子响应的实验论据，用量子理论导出高温超导薄膜探测器的，表明超导探测器的正比于超导薄膜长厚比的平方根，而与宽度无关。因此，采用超导薄膜（减小厚度），同时将薄膜光刻成弯曲线条或蛇形，增加其长度，将获得高Ｄ＊值的超导探测器。这是具有量子响应的超导探测器的重要结论。它为超导红外探测器的研制、设计提供了重要的理论依据。     

YBCO高温超导微带线的非平衡光响应及其恢复时长

研究了在波长为0.68μm的连续激光辐照下,钇钡铜氧(YBCO)高温超导(HTS)微带线的非平衡光响应特性,并从超导体机制探索和光响应超导器件研制两个角度对实验现象进行讨论。实验观察到高温超导微带线的非平衡光响应阈值,当功率小于15 mW时,以辐射热效应为主;当功率大于15 mW时,出现非平衡光响应。该阈值的发现,是对Zeldov的“热效应”与“光子效应”同时存在理论的进一步完善,并设想了一种新型的高温超导衰减器;研究了高温超导微带线非平衡光响应的恢复时长,当激光功率为45 mW时,恢复时长约为3.5 s,分析了该时长存在的机制及其对光响应超导器件二次激光激励的影响。     

新型薄膜材料在激光能量／功率计应用中的新进展

介绍了目前新型薄膜材料在激光能量／功率计应用中的最新试验研究进展。最近从实验中发现多种新型材料的薄膜具有光热辐射感生热电电压,对这种基于各向异性塞贝克效应的感生电压的性质进行详细的研究,发现并证明此类薄膜具有响应光谱宽、响应速度快、在有效范围内线性好等优点,可以应用于激光能量／功率计。     

微透镜和高Tc超导红外探测器组件

本文首次报道了利用微透镜阵列来提高ＹＢＣＯ高Ｔｃ超导薄膜红外探测器的光响应特性，介绍了利用光刻／离子束刻蚀的方法制作单片线列石英微透阵列的工艺以及制备线列ＹＢＣＯ高Ｔｃ超导薄膜红外探测器的方法，并将所制的石英微透镜阵列应用于ＹＢＣＯ超导器件。     

波段内激光辐照光电探测器的光热效应实验研究

以1.06μm激光为例,使用PC型HgCdTe探测器,从实验的角度全面给出探测器各种可能的激光响应结果;同时给出响应波段内激光辐照探测器时光、热各自作用及光热综合作用的实验曲线,并结合此结果以清晰直观的图像分析了波段内激光辐照光电探测器时各种响应结果的成因.研究表明:激光辐照过程中,探测器信号响应曲线是光、热综合作用的竞争结果;激光停照后,信号曲线仅反映探测器的热恢复过程;光电导探测器的光响应和热响应随工作温度的变化均存在峰值响应.探测器的工作温度、激光功率密度和辐照时间是影响探测器信号响应曲线行为的关键参数.     

线列混合型石英微透镜/红外探测器阵列的研究

阐述了利用离子束刻蚀技术制作线列长方状拱面石英微透镜阵列的工艺方法，对所制微光学元件的光学性能进行了测试和讨论，所制成的石英微透镜阵列器件在线列ＹＢａ２Ｃｕ３Ｏ７－δ高Ｔｃ超导薄膜红外探测器上得到了应用。实验结果表明，混合型的石英微透镜／红外探测器结构显著改善了线列ＹＢＣＯ高温超导薄膜红外探测器的光响应特性。     

Y－Ba－Cu－O超导薄膜在其临界温度附近的克尔效应观测

Ｙ－Ｂａ－Ｃｕ－Ｏ超导薄膜在其临界温度附近的克尔效应观测钱小陵（首都师范大学物理系，北京１０００３７）王国文（北京大学物理系，北京１００８７１）超导材料在其临界温度附近，许多物理性质都有很明显的变化，因此我们估计在磁场中的超导薄膜的表面在其临界温度附...     

由时间飞行光谱技术测量激光制膜过程中出射粒子的飞行速度

激光烧蚀沉积法是近几年迅速发展起来的新型高温超导薄膜以及超导微电子器件制备的一项重要工艺。实验研究表明,采用这种沉积方法能够实现超导薄膜的原位低温外延生长,进而易于获得性能优良的超导膜,其原因除了在制膜过程中靶面上各种元素具有     

Broad-band photoresponse from InAs quantum dots embedded into InGaAs graded well

A broad-band photoresponse is obtained from undoped InAs multiple quantum dots grown by the molecular beam epitaxy (MBE) technique on a (100) GaAs substrate. The quantum dots were embedded in an In/sub x/Ga/sub 1-x/As graded well where the In mole fraction is chosen in the range of 0.3 /spl ges/ x /spl ges/ 0.0. The photoresponse of the reversed biased device, obtained at 80.5 K and using the normal incident configuration, was found to span the spectral range of 3.5 - 9.5 /spl mu/m. While the photoresponse is significantly high under the influence of the reverse bias voltage, the forward bias photoresponse is found to be negligible.     

Anisotropic electroabsorption and optical modulation in InGaAs/InAlAs multiple quantum well structures

The first measurements to be made of large anistropic electroabsorption and modulation of long-wavelength light propagating along the plane of InGaAs/InAlAs multiple quantum well (MQW) structures grown by molecular beam epitaxy (MBE) are reported. Photocurrent response of waveguide p-i-n diodes is studied for incident light polarization parallel and perpendicular to the MQW layers. Photocurrent increase with reverse bias throughout the entire photoresponse spectrum is observed for both polarizations. The MQW p-in optical modulator shows a capacitance-limited pulse response of 250 ps and the modulation depth is 14 percent.     

Infrared detection utilizing both intersubband and free-carrier absorption in reverse-biased Superlattice infrared photodetector

Intersubband and free-carrier associated photoresponse in a GaAs-AlGaAs superlattice infrared photodetector is investigated. Under reverse bias, the photodetector is similar to an internal photoemission photodetector and significant photoresponse due to free-carrier absorption at the collector contact is found. In particular, in our photodetector, intersubband transitions at the superlattice layer also play an important role at low reverse biases and produce a photocurrent with an opposite direction to that of the free-carrier associated photocurrent. Since the total photocurrent consists of two components with opposite signs, photocurrent reversal occurs in the response spectrum. At high reverse bias, the intersubband-associated photoresponse is fully suppressed by the blocking barrier and the overall photoresponse is mainly due to the photoemission via free-carrier absorption at the collector contact. The intersubband and free-carrier associated photocurrent components under reverse bias can be resolved from the measured polarization dependence of the spectral response. The analysis of the measured free-carrier associated photocurrent agrees with previous studies on free-carrier absorption. A possible application with our detector to determine the wavelength of a monochromatic light is also demonstrated.     

Tunable photodetectors based on strain compensated GaInAsSb/AlAsSbmultiple quantum wells grown by molecular beam epitaxy

GaInAsSb/AlGaAsSb strain compensated multiple quantum well (MQW) p-i-n structures grown by molecular beam epitaxy on GaSb substrates have been successfully fabricated into tunable photodiodes, which showed a large photoresponse peak shift up to 30 meV (80 nm) at 77 K under a reverse bias of 10 V due to quantum confined Stark effect (QCSE). The QCSE persists up to room temperature and the values of the excitonic absorption peak shifts agree well with the calculated results. Based on the observed QCSE, an electrically tunable resonant cavity enhanced photodetector with strain compensated MQW structure is proposed and modeled     

Negative photocurrent in GaAs-(AlGa)As heterojunctions

A negative photoresponse in p lightly doped GaAs-n heavily doped (AlGa)As heterojunctions is observed. The a.c. spectral response is presented as a function of d.c. bias and illumination. A model for negative photocurrents is proposed as due to electron diffusion into the p side. The photoresponse sign reversal is caused by the existence of the notch-spike discontinuity and of a notch population. Estimations of the band diagram are made from photoresponse and electrical measurements.     

Negative photoresponse in modulation doped field effect transistors(MODFET's): theory and experiment

A model for the mechanism of negative photoresponse, namely, the decrease of drain current under illumination, in AlGaAs-GaAs MODFET's is presented. Also, a comprehensive experimental study discussing the dependence of this phenomena on gate and drain to source bias voltages and optical power, as well as a comparison with devices that show the usual positive photoresponse, are reported. The negative photoresponse is attributed to trapping of photogenerated carriers in the GaAs buffer layer, causing a change in the potential profile and consequent reduction in the number of carriers in the 2-DEG channel. The above theory is supported by numerical solution of Poisson's and electron continuity equation, using the finite-elements method. Finally, the implications of the negative photoresponse on the high-speed photodetection properties of MODFET's devices are discussed     

Injection behavior and modeling of 100 mW broad area diode lasers

The output from a single-frequency, narrow-linewidth GaAlAs diode laser was injected into a 100-mW broad-area diode laser. The injected laser emitted in a single longitudinal mode with up to 80 mW in a single, diffraction-limited, 0.5° FWHM far-field lobe. The angle of the far-field lobe steered with injection frequency and broad-area laser bias current, displaying behavior similar to that observed with injected gain-guided laser arrays. A Fabry-Perot amplifier model which explains the injection behavior in terms of Gaussian beam propagation in a large optical cavity is proposed. The model provides criteria for optimizing locking bandwidth, beam steering, and injection efficiency     

Room-Temperature p-n-p AlGaAsSb–InGaAsSb Heterojunction Phototransistors With Cutoff Wavelength at 2.5 $mu$ m

Novel p-n-p AlGaAsSb-InGaAsSb heterojunction phototransistors (HPTs) grown by solid-source molecular beam epitaxy have been proposed and demonstrated. The p-n-p phototransistor structure provides a higher emitter injection ratio than its n-p-n counterpart, due to the large conduction band offset and almost continuous valence band edges between InGaAsSb and AlGaAsSb quaternary alloys. The resulting HPT devices exhibit high responsivities under a bias voltage above 0.3 V. A high room-temperature spectral responsivity of 2984 A/W is achieved at 2.24 mum, corresponding to an optical gain of 1652. The 50% cutoff wavelength of spectral photoresponse at room temperature is 2.50 mum. A room-temperature specific detectivity (D^*) of 8.3times10 ¹¹ cm middot Hz^1/2/W is obtained     

Specific features of amorphous silicon layers grown by plasma-enhanced chemical vapor deposition with tetrafluorosilane

Hydrogenated amorphous silicon layers with crystalline nanoparticles have been produced by plasma-enhanced chemical vapor deposition, with tetrafluorosilane added to the gas mixture. The photoluminescence kinetics and photoelectric properties of structures based on these layers have been studied. The structures have a substantial photoresponse efficiency in the visible spectral range, with the position of the photoresponse maximum dependent on the applied bias.     

β-Ga_2O_3薄膜的分子束外延生长及其紫外光敏特性研究

采用分子束外延(MBE)方法在Al2O3(0001)基片上生长了β-Ga2O3薄膜,利用XRD、SEM和AFM对薄膜的结构和形貌特性进行了表征。制作了基于β-Ga2O3薄膜的金属-半导体-金属(MSM)结构紫外探测器并对其进行了电学特性测试,结果表明:在20 V偏压下,器件的暗电流为8 nA;在波长为254 nm、光照强度为13×10–6W/cm2的紫外光照射下,器件的光电流为624 nA;器件的光电流与暗电流比值为78,光响应度达360 A/W,表现出明显的日盲紫外光响应特性。